U.S. Pat. No. 4,819,476 describes a punch assembly for a stamping and forming machine of the type shown in U.S. Pat. No. 4,497,196. The stamping and forming machine has a punch assembly and a die assembly mounted in a housing for movement towards and away from each other in a horizontal plane. The strip material, which is in a vertical plane, is fed along a strip feed path which extends between the opposed surfaces of the punch and die assemblies so that when these assemblies move against each other, the strip is blanked or formed in accordance with the punches and dies in the punch and die assemblies. The punch assembly comprises a punch ram having the individual punches mounted, in a punch holder, on the face thereof and a stripper plate which is located in front of the ends of the punches. The stripper plate is movable from a normal extended position relatively towards the punch ram when the tooling moves against the strip material. One of the advantageous features of a punch assembly as described in U.S. Pat. No. 4,819,476 is that the ends of the punches are recessed in openings in the stripper plate when the stripper plate is in its extended position and the punches are thereby protected against damage.
Punch assemblies of the type described in the above-identified U.S. Patent are presently being used to a substantial extent and are proving to be highly advantageous as compared with conventional punch and die sets in which the punches and dies are mounted on spaced-apart die shoes which in turn are mounted in a conventional vertical stamping and forming press.
Present design practice for a punch assembly for a machine of the type described in the above noted U.S. Patents requires that the entire punch assembly be an integrated unit comprised of the ram, the punch holder, the stripper plate, and other parts such as the coupling between the stripper plate and the punch ram. When a production run of a specific stamped and formed part has been finished and when a production run of a different part is to be started, the entire punch assembly is removed from the machine and replaced by a punch assembly having the tooling required for the different part which is to be produced. The use of integrated punch assemblies to produce a given stamped and formed part is not objectionable when extremely large numbers of the parts are required; however, if relatively limited numbers of a specific stamped and formed part are required, the manufacture of an entire punch assembly can constitute a relatively high tooling cost for the product.
The present invention is directed to the achievement of a punch assembly having the punch holder, the punches, and the stripper plate mounted on the punch ram as a removable sub-assembly. The tooling, particularly the punch and stripper plate portion of the tooling, required to produce the part can, therefore, in accordance with the present invention, be made at a substantially reduced cost as compared with previous methods of making such tooling.